Dendritic cells (“DC”) are one type of antigen-presenting cell (“APC”) of the immune system. Dendritic cells typically ingest antigens by phagocytosis, pinocytosis, or via interaction with a variety of cell surface receptors and endocytosis; degrade the antigens; then present fragments of those antigens in association with MI-IC (“major histocompatibility complex”) on their surfaces that other immune cells (primarily T cells) respond to. Dendritic cells can be characterized by long “dendritic” processes (resembling dendrites in nerve cells). These cells are typically found in nonlymphoid organs, for example, the skin (where they are called Langerhans cells), nose, heart, liver, kidneys, lungs, stomach, intestines, etc., where they are able to capture antigens. It is believed that, upon capturing antigens, dendritic cells migrate through the circulation (blood and lymph) to the lymphoid organs where they can interact with T cells to induce their proliferation, activation to effectors, activation to memory, deletion (death), anergy (inactivation) or regulatory functions (e.g., Tr1, Tr2).
Lectins are glycoproteins that can bind carbohydrates. Molecular analysis of dendritic cells has revealed that they express a variety of these carbohydrate-specific proteins. It has been demonstrated that the lectins function in dendritic cells to capture and direct antigens to specialized antigen-processing compartments within the cell, via receptor-mediated endocytosis. Furthermore, there is evidence to suggest that lectin-ligand interactions can modulate cytokine production by dendritic cells as well as the maturation state of those cells. One class of lectins that often appear on dendritic cells are calcium-dependent carbohydrate binding proteins, or “C-type lectins.” Specific lectins may be expressed on each type of dendritic cell, such as the lectin Langerin on Langerhan dendritic cells, the lectin BDCA-2 on plasmacythid dendritic cells, or the lectin DC-SIGN on myeloid dendritic cells.